JP2013237841A - Hollow polymeric-alkaline earth metal oxide composite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plurality of polymeric particles embedded with alkaline-earth metal oxide, which are used for polishing pads for chemical mechanical polishing to polish a semiconductor wafer.SOLUTION: The gas-filled polymeric microelements have a shell and a density of 5 g/liter to 200 g/liter. The shell has an outer surface and a diameter of 5 to 200 μm with the outer surface of the shell of the gas-filled polymeric particles having alkaline-earth metal oxide-containing particles embedded in the polymer. The alkaline-earth metal oxide-containing particles have an average particle size of 0.01 to 3 μm, distributed within each of the polymeric microelements to coat less than 50 percent of the outer surface of the polymeric microelements.

Description

  The present invention relates to a polishing pad for chemical mechanical polishing (CMP), and more particularly to a polymer composite polishing pad suitable for polishing at least one of a semiconductor, magnetic or optical substrate.

  Semiconductor wafers with integrated circuits fabricated thereon are polished to provide an ultra-smooth and flat surface that must deviate to less than a fraction of a micron in a given plane. It must be. This polishing is typically accomplished by a chemical mechanical polishing (CMP) operation. Such a “CMP” operation utilizes a chemically active slurry that is buffed against the wafer surface by a polishing pad. The chemically active slurry and polishing pad combine to polish or planarize the wafer surface.

  One problem associated with CMP operations is wafer scratching. Certain polishing pads may contain foreign objects that cause wafer gouging or scratching. For example, foreign matter can cause chatter marks in hard materials such as TEOS insulation. For the purposes of this specification, TEOS refers to a hard glass-like insulation formed from the decomposition of tetraethyloxysilicate. This damage to the insulation can cause wafer defects and reduced wafer yield. Another scratching problem associated with foreign objects is damage to non-ferrous wiring such as copper wiring. If the pad is scratched too deep into the wiring line, the resistance of the line increases to the point where the semiconductor does not function properly. In extreme cases, such contaminants create macro scratches that can result in scraping of the entire wafer.

  Reinhardt et al. In US Pat. No. 5,572,362 describe a polishing pad that uses hollow polymer microelements instead of glass globules to form pores in a polymer matrix. The advantages of this design are uniform polishing, low defect rate and improved removal rate. The Reinhardt et al. IC1000® polishing pad design outperforms the previous IC60 pad in terms of scratching by using a polymer shell instead of a glass shell. In addition, Reinhardt et al. Found an unexpected maintenance of planarization efficiency with the use of softer polymer microspheres instead of hard glass spheres. The Reinhardt et al. Polishing pad has long served as an industry standard for CMP polishing and has played an important role in advanced CMP applications.

  Another set of problems associated with CMP operations is pad-to-pad variation, such as density variation and intra-pad variation. To address these issues, polishing pad manufacturers have relied on careful molding techniques that use controlled cure cycles. These efforts focused on the macro properties of the pad, but did not address the macro polishing aspect associated with polishing pad materials.

  There is an industry need for a polishing pad that provides an improved combination of planarization, removal rate and scratching. In addition, there remains a need for a polishing pad that provides these properties in a polishing pad while reducing pad-to-pad variation.

  An aspect of the present invention is a plurality of polymer particles embedded with alkaline earth metal oxide, comprising gas filled polymer microelements, wherein the gas filled polymer microelements have a shell and a density of 5 g / liter to 200 g / liter. The shell has an outer surface and a diameter of 5 μm to 200 μm, and the outer surface of the shell of the gas-filled polymer particles has alkaline earth metal oxide-containing particles embedded in the polymer, the alkaline earth metal oxide The contained particles have an average particle size of 0.01 to 3 μm, the alkaline earth metal oxide-containing particles are dispersed in each polymer microelement, and the alkaline earth metal oxide-containing region is a polymer microelement Less than 50% of the outer surface of the polymer, and the total of the polymer microelements is less than 0.1% by weight, i) alkaline earth having a particle size greater than 5 μm Metal oxide-containing particles, ii) an alkaline earth metal oxide-containing region covering more than 50% of the outer surface of the polymer microelement, and iii) an average of greater than 120 μm aggregated with the alkaline earth metal oxide-containing particles It includes a plurality of polymer particles associated with polymer microelements that are cluster-sized.

  Another aspect of the present invention is a plurality of polymer particles embedded with alkaline earth metal oxide, comprising gas filled polymer microelements, wherein the gas filled polymer microelements are between the shell and 10 g / liter to 100 g / liter. The shell has an outer surface and a diameter of 5 μm to 200 μm, the outer surface of the shell of the gas-filled polymer particles has alkaline earth metal oxide-containing particles embedded in the polymer, and the alkaline earth The metal oxide-containing particles have an average particle size of 0.01 to 2 μm, the alkaline earth metal oxide-containing particles are dispersed in each polymer microelement, and the alkaline earth metal oxide-containing region is Discrete to coat 1-40% of the outer surface of the polymer microelements, with a total of less than 0.1% by weight of the polymer microelements having i) a particle size greater than 5 μm Alkaline earth metal oxide-containing particles, ii) Alkaline earth metal oxide-containing regions covering more than 50% of the outer surface of the polymer microelements, and iii) Aggregating with alkaline earth metal oxide-containing particles, from 120 μm A plurality of polymer particles associated with polymer microelements, which also have a larger average cluster size.

A side sectional view of a Coanda block air classifier is shown. A front sectional view of a Coanda block air classifier is shown. 1,500 times SEM of polyacrylonitrile / methacrylonitrile shell embedded with magnesium oxide / calcium particles. 100X SEM of fine polyacrylonitrile / methacrylonitrile shell coated with magnesium oxide / calcium particles. It is a 100 times SEM of a polyacrylonitrile / methacrylonitrile shell embedded with magnesium oxide calcium particles after separation of fine and coarse fractions. It is a 100 times SEM of polyacrylonitrile / methacrylonitrile shell agglomerates and rice grain-shaped magnesium oxide / calcium particles. FIG. 4 is a plot of pad density vs. position for polishing pads containing poly (vinylidene dichloride) / polyacrylonitrile / silica shell and polishing pads containing polyacrylonitrile / methacrylonitrile / magnesium oxide / calcium shell. 250X SEM of poly (vinylidene dichloride) / polyacrylonitrile / silica shell in polyurethane matrix. 250 times SEM of polyacrylonitrile / methacrylonitrile / magnesium oxide calcium shell in polyurethane matrix. 250 SEM of poly (vinylidene dichloride) / polyacrylonitrile / silica shell in the polyurethane matrix after skiving. SEM of 250 times the polyacrylonitrile / methacrylonitrile / magnesium oxide / calcium shell in the polyurethane matrix after skiving. 10 is a shear modulus plot of Comparative Examples B and C and Example 10. FIG. 2 is a plot showing the toughness of a pad without a shell, a pad with poly (vinylidene dichloride) / polyacrylonitrile / silica, and a pad with a polyacrylonitrile / methacrylonitrile / magnesium oxide and calcium shell. 5 is a 250-fold SEM showing the fracture mode of Comparative Example C. 5 is a SEM of 250 times showing the fracture mode of Example 10.

Detailed Description of the Invention The present invention provides a method of forming a composite alkaline earth metal oxide-containing polishing pad useful for polishing semiconductor substrates. The polishing pad comprises a polymer matrix, hollow polymer microelements and alkaline earth metal oxide-containing particles embedded in the polymer microelements. The alkaline earth element is preferably calcium oxide, magnesium oxide or a mixture of magnesium oxide and calcium oxide. Surprisingly, alkaline earth metal oxide-containing particles, when classified into specific structures associated with polymer microelements, tend not to cause excessive scratching or gouging for advanced CMP applications. This suppression of gouging and scratching is obtained despite the polymer matrix having alkaline earth metal oxide-containing particles on its polished surface.

  Common polymer polishing pad matrix materials include polycarbonate, polysulfone, polyamides, ethylene copolymers, polyethers, polyesters, polyether-polyester copolymers, acrylic polymers, polymethyl methacrylate, polyvinyl chloride, polycarbonate, polyethylene copolymers, There are polybutadienes, polyethyleneimines, polyurethanes, polyethersulfones, polyetherimides, polyketones, epoxy resins, silicones, copolymers and mixtures thereof. Preferably, the polymeric material is a polyurethane and may be either a crosslinked polyurethane or a non-crosslinked polyurethane. For the purposes of this specification, “polyurethanes” refers to products derived from difunctional or polyfunctional isocyanates such as polyetherureas, polyisocyanurates, polyurethanes, polyureas, polyurethaneureas, Copolymers of these and their mixtures.

  Preferably, the polymeric material is a block or segmented copolymer that can be separated into a phase rich in one or more blocks or segments of the copolymer. Most preferably, the polymeric material is a polyurethane. Cast molded polyurethane matrix materials are particularly suitable for planarizing semiconductor, optical and magnetic substrates. A technique for controlling the polishing properties of the pad is to change its chemical composition. In addition, the choice of raw materials and manufacturing method affects the polymer morphology and the final properties of the materials used to make the polishing pad.

  Preferably, urethane production involves the preparation of terminal isocyanate-modified urethane prepolymers from polyfunctional aromatic isocyanates and prepolymer polyols. For the purposes of this specification, the term prepolymer polyol includes diols, polyols, polyol-diols, copolymers thereof and mixtures thereof. Preferably, the prepolymer polyols are selected from the group consisting of polytetramethylene ether glycol [PTMEG], polypropylene ether glycol [PPG], ester-based polyols such as ethylene or butylene adipates, copolymers thereof and mixtures thereof. The Exemplary polyfunctional aromatic isocyanates include 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, 4,4′-diphenylmethane diisocyanate, naphthalene-1,5-diisocyanate, tolidine diisocyanate, paraphenylene diisocyanate, There are xylylene diisocyanates and mixtures thereof. The polyfunctional aromatic isocyanates contain less than 20% by weight of aliphatic isocyanates such as 4,4'-dicyclohexylmethane diisocyanate, isophorone diisocyanate and cyclohexane diisocyanate. Preferably, the polyfunctional aromatic isocyanates contain less than 15 wt% aliphatic isocyanates, more preferably less than 12 wt%.

  Exemplary prepolymer polyols include polyether polyols such as poly (oxytetramethylene) glycol, poly (oxypropylene) glycol and mixtures thereof, polycarbonate polyols, polyester polyols, polycaprolactone polyols and their There is a mixture. Exemplary polyols are ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,2-butanediol, 1,3-butanediol, 2-methyl-1,3-propanediol, 1 , 4-butanediol, neopentyl glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, tripropylene glycol and mixtures thereof And low molecular weight polyols.

Preferably, the prepolymer polyols are selected from the group consisting of polytetramethylene ether glycol, polyester polyols, polypropylene ether glycols, polycaprolactone polyols, copolymers thereof and mixtures thereof. If the prepolymer polyols are PTMEG, copolymers thereof or mixtures thereof, the terminal isocyanate modified reaction product preferably has a weight percent unreacted NCO range of 8.0 to 20.0. For polyurethanes formed of PTMEG or PTMEG blended with PPG, the preferred weight% NCO is in the range of 8.75 to 12.0, most preferably in the range of 8.75 to 10.0. Specific examples of PTMEG-based polyols are Invista's Terathane® 2900, 2000, 1800, 1400, 1000, 650 and 250, Lyondell's Polymeg® 2900, 2000, 1000, 650, BASF's PolyTHF® Trademarks) 650, 1000, 2000 and low molecular weight species such as 1,2-butanediol, 1,3-butanediol and 1,4-butanediol. If the prepolymer polyol is PPG, a copolymer thereof or a mixture thereof, the terminal isocyanate-modified reaction product most preferably has a weight percent unreacted NCO range of 7.9 to 15.0. Specific examples of PPG polyols are Bayer's Arcol® PPG-425, 725, 1000, 1025, 2000, 2025, 3025 and 4000, Dow's Voranol® 1010L, 2000L and P400, all from Bayer. The product lines are Desmophen® 1110BD, Acclaim® Polyol 12200, 8200, 6300, 4200, 2200. If the prepolymer polyol is an ester, a copolymer thereof or a mixture thereof, the terminal isocyanate modified reaction product most preferably has a weight percent unreacted NCO range of 6.5 to 13.0. Specific examples of ester polyols are Polyurethane Specialties Company Inc. Millester 1, 11, 2, 23, 132, 231, 272, 4, 5, 510, 51, 7, 8, 9, 10, 16, 253, Bayer of Desmophen ^{(R) 1700,1800,2000,2001KS, 2001K 2, 2500,2501,2505,2601,} PE65B, Rucoflex S-1021-70 of Bayer, S-1043-46, a S-1043-55.

  In general, the prepolymer reaction product is reacted or cured with a curing agent polyol, polyamine, alcohol amine or mixtures thereof. For purposes of this specification, polyamines include diamines and other multifunctional amines. Exemplary curing agent polyamines include aromatic diamines or polyamines such as 4,4'-methylene-bis-o-chloroaniline [MBCA], 4,4'-methylene-bis- (3-chloro- 2,6-diethylaniline) [MCDEA], dimethylthiotoluenediamine, trimethylene glycol di-p-aminobenzoate, polytetramethylene oxide di-p-aminobenzoate, polytetramethylene oxide mono-p-aminobenzoate, polypropylene oxide Di-p-aminobenzoate, polypropylene oxide mono-p-aminobenzoate, 1,2-bis (2-aminophenylthio) ethane, 4,4'-methylene-bis-aniline, diethyltoluenediamine, 5-tert-butyl -2,4- and 3-tert-butyl-2 6- toluenediamine, there are 5-tert-amyl-2,4- and 3-tert-amyl-2,6-toluenediamine and chlorotoluene diamine. In some cases, it is also possible to produce urethane polymers for polishing pads in a single mixing step that avoids the use of prepolymers.

  The polymer components used to make the polishing pad are preferably selected so that the resulting pad morphology is stable and easy to reproduce. For example, when 4,4'-methylene-bis-o-chloroaniline [MBCA] is mixed with a diisocyanate to form a polyurethane polymer, it is often advantageous to control the levels of monoamines, diamines and triamines. Controlling the proportions of mono-, di- and triamines helps to maintain the chemical ratio and resulting polymer molecular weight within a consistent range. In addition, for consistent manufacturing, it is often important to control additives such as antioxidants and impurities such as water. For example, water reacts with isocyanate to form gaseous carbon dioxide, so controlling the concentration of water can affect the concentration of carbon dioxide bubbles that form pores in the polymer matrix. The isocyanate reaction with exogenous water also reduces the isocyanate available for reaction with the chain extender, thus reducing the stoichiometric ratio as well as the level of crosslinking (if there are excess isocyanate groups) and the resulting polymer molecular weight. Change.

  The polyurethane polymer material is preferably formed from a prepolymer reaction product of toluene diisocyanate and polytetramethylene ether glycol and aromatic diamines. Most preferably, the aromatic diamine is 4,4'-methylene-bis-o-chloroaniline or 4,4'-methylene-bis- (3-chloro-2,6-diethylaniline). Preferably, the prepolymer reaction product has 6.5 to 15.0% by weight unreacted NCO. Examples of suitable prepolymers within this unreacted NCO range are Imuthane® prepolymers PET-70D, PHP-70D, PET-75D, PHP-75D, PPT-75D, PHP from COIM USA, Inc. Adiprene® prepolymers LFG740D, LF700D, LF750D, LF751D, LF753D, L325 from -80D and Chemtura. In addition, blends of other prepolymers other than those described above may be used to reach the appropriate% unreacted NCO level as a result of the blend. Many of the prepolymers described above, such as LFG740, LF700D, LF750D, LF751D, and LF753D, have less than 0.1% by weight free TDI monomer and have a lower release with a more consistent prepolymer molecular weight distribution than conventional prepolymers. Isocyanate prepolymers, thus facilitating the formation of polishing pads having excellent polishing properties. This improved prepolymer molecular weight consistency and low free isocyanate monomer provides a more regular polymer structure and contributes to improved polishing pad consistency. For most prepolymers, the low free isocyanate monomer is preferably less than 0.5% by weight. In addition, “conventional” prepolymers having higher levels of reaction (ie, two or more polyols each terminated with a diisocyanate) and higher levels of free toluene diisocyanate prepolymers have similar results. Should be put out. In addition, low molecular weight polyol additives such as diethylene glycol, butanediol and tripropylene glycol facilitate control of the weight percent unreacted NCO of the prepolymer reaction product.

  Similarly, polyurethane polymer materials can also be formed from prepolymer reaction products of 4,4-diphenylmethane diisocyanate (MDI) and polytetramethylene glycol and diols. Most preferably, the diol is 1,4-butanediol (BDO). Preferably, the prepolymer reaction product has 6 to 13 wt% unreacted NCO. Examples of suitable prepolymers within this unreacted NCO range are Imuthane 27-85A, 27-90A, 27-95A, 27-52D, 27-58D from COIM USA and Andur® LE-LE from Anderson Development Company 75AP, IE80AP, IE90AP, IE98AP, IE110AP prepolymer.

In addition to controlling weight percent unreacted NCO, curative prepolymer reaction product is generally, OH or NH _2: stoichiometric ratio from 85 to 115% of unreacted NCO, preferably a 90 to 110% . This stoichiometric ratio can be achieved directly by providing a stoichiometric level of the feedstock, or by reacting a portion of the NCO with water intentionally or by exposure to exogenous moisture. It can also be achieved indirectly.

  The polymer matrix contains polymer microelements dispersed within the polymer matrix and on the polishing surface of the polymer matrix. The polymer microelement has an outer surface and is filled with fluid to form a texture on the polished surface. The fluid filling the matrix can be a liquid or a gas. If the fluid is a liquid, the preferred fluid is water, for example distilled water containing only accidental impurities. If the fluid is a gas, air, nitrogen, argon, carbon dioxide or combinations thereof are preferred. For some microelements, the gas may be an organic gas, such as isobutane. Gas filled polymer microelements typically have an average size of 5 to 200 microns. Preferably, the gas filled polymer microelement generally has an average size of 10 to 100 microns. Most preferably, the gas filled polymer microelement generally has an average size of 10 to 80 microns. Although not necessarily, the polymeric microelements preferably have a spherical shape or represent a microsphere. Thus, if the microelement is spherical, the average size range also represents the diameter range. For example, an average diameter range of 5 to 200 microns, preferably 10 to 100 microns, and most preferably 10 to 80 microns.

  The polishing pad includes an alkaline earth metal (Group IIA) oxide-containing region dispersed within each polymer microelement. These alkaline earth metal oxide-containing regions may be particles or have an elongated alkaline earth metal oxide-containing structure. Generally, the alkaline earth metal oxide-containing region represents particles embedded or attached to the polymer microelement. The average particle size of the alkaline earth metal oxide-containing particles is generally 0.01 to 3 μm. Preferably, the average particle diameter of the alkaline earth metal oxide-containing particles is 0.01 to 2 μm. These alkaline earth metal oxide-containing particles are discrete so as to coat less than 50% of the outer surface of the polymer microelement. Preferably, the alkaline earth metal oxide-containing region covers 1-40% of the surface area of the polymer microelement. Most preferably, the alkaline earth metal oxide-containing region covers 2-30% of the surface area of the polymer microelement. The alkaline earth metal oxide-containing microelement has a density of 5 g / liter to 200 g / liter. In general, alkaline earth metal oxide-containing microelements have a density of 10 g / liter to 100 g / liter.

  In order to avoid an increase in scratching or gouging, it is important to avoid alkaline earth metal oxide-containing particles having an unfavorable structure or morphology. These undesirable alkaline earth metal oxide-containing particles should total less than 0.1% by weight of the polymer microelements. Preferably, these undesirable alkaline earth metal oxide-containing particles should total less than 0.05% by weight of the polymer microelements. The first type of disadvantageous alkaline earth metal oxide-containing particles are alkaline earth metal oxide-containing particles having a particle size greater than 5 μm. These alkaline earth metal oxide-containing particles are known to cause chatter defects in TEOS wafers and scratch and gouging defects in copper wiring. A second type of inconvenient alkaline earth metal oxide-containing particles is an alkaline earth metal oxide-containing region that covers more than 50% of the outer surface of the polymer microelement. These microelements, including large alkaline earth metal oxide-containing surface areas, can also scratch or move within the microelements, creating chatter defects in TEOS wafers, and scratching and gouging in copper interconnects. Defects can be created. A third type of disadvantageous alkaline earth metal oxide-containing particles is agglomerates. Specifically, the polymer microelements can agglomerate with alkaline earth metal oxide-containing particles to an average cluster size greater than 120 μm. An aggregate size of 120 μm is common for microelements having an average diameter of about 40 μm. Larger microelements form larger agglomerates. Alkaline earth metal oxide-containing particles having this morphology can cause visible and scratching defects even in sensitive polishing operations.

  Air classification can be useful for producing composite alkaline earth metal oxide-containing polymer microelements that have a minimum of disadvantageous alkaline earth metal oxide-containing particle species. Unfortunately, alkaline earth metal oxide-containing polymer microelements often have different densities, different wall thicknesses and different particle sizes. In addition, the polymer microelement has various alkaline earth metal oxide-containing regions dispersed on its outer surface. Therefore, there are a number of challenges in separating polymer microelements having various wall thicknesses, particle sizes and densities, and numerous attempts at centrifugal air classification and particle sorting have failed. These methods, at best, are useful for removing one unwanted component from a feedstock such as fines. For example, since many of the alkaline earth metal oxide-containing microspheres have the same size as the desired alkaline earth metal oxide-containing composite, it is difficult to separate them using a screening method. However, it has been found that separators that work with a combination of inertia, gas or airflow resistance and the Coanda effect can provide effective results. The Coanda effect is that if a wall is placed on one side of the jet, the jet will tend to flow along the wall. Specifically, when the gas-filled microelement is passed through a gas jet while adjoining the curved wall of the Coanda block, the polymer microelement is separated. Coarse polymer microelements are separated from the curved wall of the Coanda block and the polymer microelements are purified by two-way separation. If the feedstock contains alkaline earth metal oxide-containing fines, the method separates the polymer microelements from the alkaline earth metal oxide-containing fines by the Coanda block walls so that the fines travel along the Coanda block. Additional steps can also be included. In the three-way separation, the coarse powder is separated from the Coanda block to the maximum distance, the intermediate or purified product is separated to the intermediate distance, and the fine powder travels along the Coanda block. Matsubo Co., Ltd. manufactures elbow jet air classifiers that utilize these features for effective particle separation. In addition to the feed jet, the Matsubo classifier provides two additional steps that feed two additional air streams into the polymer microelements to facilitate separation of the polymer microelements from coarse particles associated with the polymer microelements.

  Separation of coarse particles associated with alkaline earth metal oxide-containing fines and polymer microelements advantageously takes place in a single step. One pass is effective to remove both coarse and fine material, but in various orders, eg, first coarse pass, second coarse pass, then first fine pass and second pass Separation can be repeated in a fine pass. In general, however, the cleanest results result from two- or three-way separation. A further disadvantage of three-way separation is yield and cost. The feedstock generally contains more than 0.1% by weight of disadvantageous alkaline earth metal oxide-containing particles. Furthermore, it is effective with feedstocks containing more than 0.2% by weight of undesirable alkaline earth metal oxide-containing particles and more than 1% by weight.

  After separating or purifying the polymer microelements, the polymer microelements are inserted into a liquid polymer matrix to form a polishing pad. Common means for inserting polymer microelements into the pad include pouring, extrusion, aqueous solvent displacement and aqueous dispersion polymers. Mixing improves the dispersion of polymer microelements in the liquid polymer matrix. After mixing, the polymer matrix is dried or cured to form a polishing pad suitable for grooving, drilling or other polishing pad finishing operations.

  Referring to FIGS. 1A and 1B, the elbow jet air classifier has a width “w” between two side walls. Air or other suitable gas, such as carbon dioxide, nitrogen or argon, flows through openings 10, 20 and 30 to generate a jet stream around Coanda block 40. When polymer microelements are injected by a feeder 50, such as a pump or vibratory feeder, the polymer microelements enter a jet stream that initiates the classification process. In the jet stream, inertia, drag (or stream resistance) and Coanda effect forces combine to separate the particles into three sections. The fine powder 60 flows along the Coanda block. The medium-sized alkaline earth metal oxide-containing particles have sufficient inertia to overcome the Coanda effect and are collected as the purified product 70. Finally, coarse particles 80 travel a maximum distance and separate from intermediate particles. The coarse particles comprise i) alkaline earth metal oxide-containing particles having a particle size greater than 5 μm, ii) an alkaline earth metal oxide-containing region covering more than 50% of the outer surface of the polymer microelement, and iii) alkali It includes a combination of polymer microelements aggregated with earth metal oxide-containing particles to an average cluster size greater than 120 μm. These coarse particles have a negative impact on wafer polishing, particularly patterned wafer polishing for advanced nodes. The interval or width of the classifier determines the fraction that is separated into each section. Alternatively, the fines collector can be closed and the polymer microelements can be separated into two fractions, a crude fraction and a purified fraction.

Separation Separation of samples of polyacrylonitrile and methacrylonitrile isopentane-filled copolymers having an average diameter of 40 microns and a density of 30 g / liter was performed on a Matsubo Elbow Jet Air Classifier (Model EJ1S-3S). These hollow microspheres contained magnesium oxide / calcium containing particles embedded in the copolymer. The magnesium oxide / calcium containing particles covered about 5-15% of the outer surface area of the microspheres. In addition, the sample is a copolymer microsphere associated with magnesium oxide calcium particles having a particle size greater than 5 μm, ii) a magnesium oxide / calcium containing region covering more than 50% of the outer surface of the polymer microelement, and iii) It contained polymer microelements aggregated with magnesium oxide / calcium containing particles to an average cluster size greater than 120 μm. The elbow jet air classifier included the Coanda block and the structure of FIGS. 1A and 1B. FIG. 2 shows the desired magnesium oxide / calcium containing microspheres in the presence of microparticles. For the desired microspheres, the white area represents magnesium oxide / calcium oxide mineral particles embedded in the polymer shell. In the case of unwanted particles, the white area covers more than half of the particles or the entire particle. The results in Table 1 were obtained when polymer microspheres were fed through a vibratory feeder into a gas jet with the selected settings.

  The data in Table 1 shows effective removal of fines [F] and coarse material [G]. Example 7 provided 7 wt% fines and 0.2 wt% coarse material. Example 8, which is an extension experiment of Example 7, produced 8.7% by weight of fine powder and 0.7% by weight of coarse powder. The coarse material is a copolymer microsphere associated with magnesium oxide / calcium containing particles having a particle size greater than 5 μm, ii) a magnesium oxide / calcium containing region covering more than 50% of the outer surface of the polymer microelement, and iii) oxidation. It contained polymer microelements aggregated with magnesium / calcium containing particles to an average cluster size greater than 120 μm.

  3-5, FIG. 3 shows fine powder [F], FIG. 4 shows purified magnesium oxide / calcium-containing polymer microspheres [M], and FIG. 5 shows the conditions of Examples 7 and 8. Shows coarse powder [G]. The fines appear to have a particle size distribution containing only a small percentage of medium size polymer microelements. The coarse fraction contains polymer microelements with visible microelement agglomerates and magnesium oxide-calcium containing regions that cover more than 50% of the outer surface. The intermediate fraction does not appear to contain most of the fine and coarse polymer microelements. These SEM micrographs show the dramatic differences achieved by classification into three segments.

Effect on Pad Density Table 2 provides a microsphere formulation for casting a polyurethane cake used to make a polishing pad.

Controlled mixing of terminal isocyanate-modified urethane prepolymer (Adiprene® L325 from Chemtura Corporation, 9.1% NCO) with 4,4'-methylene-bis-o-chloroaniline (MBCA) as curing agent A polyurethane cake was prepared by The prepolymer temperature and curing agent temperature were 51 ° C. and 116 ° C., respectively. The ratio of prepolymer to curing agent was set so that the stoichiometric ratio defined by the ratio of NH ₂ groups in the curing agent to NCO groups in the prepolymer was 87%. These formulations show the effect of adding various polymer microspheres to a hard polymer matrix. Specifically, when no polymer microspheres are added, the hardness of the Adiprene L325 / MBOCA polymer matrix is 72 Shore D, and at the level of polymer microspheres added in the above examples, the hardness is 55-60D Shore D. To drop.

  Pore was introduced into the formulation by adding microspheres so that the average density of the pads from Comparative Example A and Comparative Example B were equal. In Comparative Example A, a poly (vinylidene dichloride) / polyacrylonitrile shell wall interspersed with silica particles was used as a pore former. In the case of Example 1, a polyacrylonitrile / methacrylonitrile shell interspersed with magnesium oxide and calcium was used. Both shell walls had the same average microsphere diameter of 40 microns. Prior to blending, the polyacrylonitrile / methacrylonitrile particles were classified using the processing techniques and conditions described above.

  A high shear mixing head was used to mix the prepolymer, curing agent and microspheres simultaneously. After exiting the mixing head, the mixed ingredients were dispensed into a 34 inch (86.4 cm) diameter circular mold over 4 minutes to give a total pour thickness of about 2 inches (5.1 cm). . The components are allowed to gel for 15 minutes and then placed in a curing oven and then cycled as follows: constant temperature increase from ambient temperature to a set temperature of 104 ° C., 15.5 hours at 104 ° C. and set temperature reduced to 21 ° C. 2 Cured in hours.

  The molded article was then “skived” (cut using a movable blade) into about 20 thin sheets of 80 mil (2.0 mm) thickness at a temperature of 70-80 ° C. Skiving started from the top of the cake, discarding incomplete sheets. (Then each sheet can then be converted to a polishing pad by grooving or drilling macrotexture on its surface and laminating it on a compressible subpad).

  The density was determined by measuring the weight, thickness and diameter of each sheet according to ASTM standard D1622. FIG. 6 shows the density of each sheet from the top to the bottom of the molded product.

The amount of polymer microspheres added was adjusted to achieve the same level of porosity and density on average throughout the molding. In the case of Comparative Example A and Example 1, the average density of all sheets of both molded articles was the same at 0.809 g / cm ³ .

  However, since the chemical reaction between the prepolymer and the curing agent is exothermic, there was a strong temperature gradient through the molded product such that the lower region of the molded product was cooler than the middle or upper region. The exothermic temperature of this prepolymer / curing agent combination exceeded the softening temperature (Tg) of the shell wall. Since these temperatures were achieved when the molded article was still gelled, in response to higher temperatures, the polymer microsphere particles increased in diameter and developed a profile of porosity within the molded article. This profile was noticeable for the cooler lower sheet cut from the molded article. The lower layer sheet has a higher density than the remaining sheets, and may become out of specification and fail, resulting in a decrease in production yield. Advantageously, all pads have a density or specific gravity within 5%. Most advantageously, the pads can be removed, leaving all pads with a density or specific gravity that varies by less than 2%.

  In FIG. 6, Comparative Example A clearly illustrates this problem. When poly (vinylidene dichloride) / polyacrylonitrile was used as the pore former, the density of the underlying layer was significantly higher than the target average density value and had to be rejected. In contrast, substituting polyacrylonitrile / methacrylonitrile in the same polymer matrix formulation (Example 9) significantly reduced the change in density from the top to the bottom of the cake and greatly reduced the occurrence of substandard density values. . The enhanced performance of polyacrylonitrile / methacrylonitrile microspheres over poly (vinylidene dichloride) / polyacrylonitrile appears to be a direct result of their higher shell wall softening temperature. As described above, as shown in Table 2, the Tg of polyacrylonitrile / methacrylonitrile microspheres is 20 ° C. higher than that of poly (vinylidene dichloride) / polyacrylonitrile, which has the effect of expanding in response to a high exothermic temperature. Reduced. The polyacrylonitrile / methacrylonitrile shell also provided the additional advantage of being a chlorine-free polymer.

  7 and 8 show cross-sectional SEMs of the sheets of Comparative Example A and Example 9, respectively. A comparison of FIGS. 7 and 8 shows that the pore sizes are very similar. These figures also show that in each case the microspheres are uniformly dispersed in the polymer matrix. The subtle difference between the two figures is the presence of more shell wall fragments that are present in the case of polyacrylonitrile / methacrylonitrile microspheres. This indicates a shell wall that is less elastic and more brittle.

Skiving comparison The difference is more pronounced in the case of skived surfaces as shown in FIGS. The skiving operation applies greater mechanical stress and is more likely to destroy the microspheres, especially if the shell wall is less ductile and the shell wall is more brittle.

  More brittle particles can break down into smaller pieces during subsequent diamond conditioning and polishing. This generates smaller polishing debris. Smaller polishing debris is less likely to scratch the semiconductor wafer and produce a fatal defect that can result in a defective wafer.

  The surface roughness of the skived surface shown in FIGS. 9 and 10 was measured by a contact method using a Zeiss profilometer (model Sufcom 1500). A 2 micron tip diamond needle (DM43801) was tracked to the pad surface and the main surface roughness parameters were measured. These parameters are average surface roughness (Ra), peak height reduction (Rpk), core roughness depth (Rk) and core roughness depth as defined in “Introduction to Surface Roughness and Scattering” by Bennett and Mattsson. It included valley depth reduction (Rvk).

  Table 3 summarizes the roughness values of Comparative Example A and Example 1.

  All roughness parameters were higher for the pads containing polyacrylonitrile / methacrylonitrile microspheres. In general, higher surface roughness results in higher removal rates during polishing and thus increased wafer throughput.

Effect of microelements on pad properties in soft formulations The following example adds either 40 micron diameter poly (vinylidene dichloride) / polyacrylonitrile or polyacrylonitrile / methacrylonitrile microspheres to a much softer matrix Show the effect of The formulation and processing conditions are summarized in Table 4.

  In these formulations, the prepolymer (Imuthane® 27-95A from COIM USA Inc.) used was a polyether system end-modified with 4,4′-diphenylmethane diisocyanate (MDI). Cured with 4-butanediol. A small amount of amine catalyst (Air products Dabco® 33-LV) was used to promote the urethane reaction. These formulations were prepared in the laboratory by intimately mixing the prepolymer, curing agent and microspheres using a vortex mixer. After mixing, the mixture was poured into an aluminum mold and cured at a high temperature to form a sheet having a width of about 12 cm, a length of about 20 cm, and a thickness of about 2 mm for determining physical properties.

  Table 5 summarizes the main physical properties of the formulations of Table 5.

  The addition of polymer microspheres to the polymer reduces both hardness and density, and comparison between Comparative Example C and Example 10 reveals that there is little difference between the addition of any microsphere formulation. is there.

  However, the different softening temperatures of poly (vinylidene dichloride) / polyacrylonitrile and polyacrylonitrile / methacrylonitrile microspheres affect the pad modulus at high temperatures. As stated earlier, the polyacrylonitrile / methacrylonitrile shell had a higher softening temperature than the poly (vinylidene dichloride) / polyacrylonitrile shell. This has the effect of maintaining higher modulus values at high temperatures, as shown by the dynamic mechanical data in FIG. During polishing, the rugged tip of the pad surface may be locally heated by polishing friction and soften excessively. A higher modulus advantageously increases the life of the irregularities and reduces the need to regenerate the irregularities by diamond conditioning.

  The tensile data shown in Table 5 is unexpected and advantageous. Normally, when pores are introduced into a polymer, all tensile properties such as modulus, tensile strength, elongation at break and toughness are reduced. This is not the case for the formulation in Table 4. As expected, the modulus decreases with the addition of polymer microspheres. However, the tensile strength decreases only in the case of poly (vinylidene dichloride) / polyacrylonitrile microspheres, and the addition of poly (vinylidene dichloride) / polyacrylonitrile microspheres or especially polyacrylonitrile / methacrylonitrile microspheres breaks. Increase point elongation and toughness values (toughness was measured as the area under the stress-strain curve). The toughness values are plotted in FIG.

  Comparison of Comparative Examples B, C and Example 10 shows that the addition of polyacrylonitrile / methacrylonitrile microspheres compared to the addition of poly (vinylidene dichloride) / polyacrylonitrile and a non-porous control. ) Shows that the pad toughness is suitably increased. This behavior suggests that the microspheres are well adhered to the surrounding polymer matrix and that more energy is required to break the pad formulation containing polyacrylonitrile / methacrylonitrile microspheres. To do.

  Dog-bone samples used to obtain tensile data were examined after scanning by microscopic scanning electron microscopy. After the test, there was residual strain in a narrow area of the dogbone. Pictures taken perpendicular to the strain direction were used to provide insight into the failure mode.

  13 and 14 show the damage behavior of Comparative Example C and Example 10. In either case, there were no voids that would correspond to the microspheres separated from the polymer matrix. This supports the above suggestion that the microspheres are well adhered. However, in FIG. 14, there are many shell fragments in the pore structure. When the pad stretches, the well-adhered microsphere shell wall also stretches, but due to its higher Tg and thus the stiffer polymer structure, the shell wall breaks but adheres to the surrounding polymer matrix. Remains. As additional energy is required to break the shell wall, the toughness value is significantly increased.

  The polishing pad of the present invention includes magnesium oxide-calcium containing particles dispersed in a consistent and uniform structure to reduce polishing defects. In particular, the composite particle structure of the claimed invention can reduce gouging and scratching defects in the case of copper polishing using a cast molded polyurethane polishing pad. In addition, air classification can provide a more consistent product with less density and less variation within the pad.

Claims (8)

A plurality of polymer particles embedded with an alkaline earth metal oxide,
A gas-filled polymer microelement, wherein the gas-filled polymer microelement has a shell and a density of 5 g / liter to 200 g / liter, the shell has an outer surface and a diameter of 5 μm to 200 μm; The outer surface of the shell has alkaline earth metal oxide-containing particles embedded in the polymer, the alkaline earth metal oxide-containing particles have an average particle size of 0.01 to 3 μm, Alkaline earth metal oxide-containing particles are dispersed in each of the polymer microelements, and the alkaline earth metal oxide-containing regions are discrete so as to coat less than 50% of the outer surface of the polymer microelements. Less than 0.1% by weight of the polymer microelements i) alkaline earth metal oxide-containing particles having a particle size greater than 5 μm, ii) Alkaline earth metal oxide-containing region covering more than 50% of the outer surface of the limer microelement, and iii) polymer microparticles aggregated with alkaline earth metal oxide-containing particles to an average cluster size greater than 120 μm A plurality of polymer particles associated with the element.   The plurality of polymer particles of claim 1, wherein the gas-filled polymer microelement is a copolymer of polyacrylonitrile and methacrylonitrile filled with isopentane.   The plurality of polymer particles of claim 1, wherein the gas-filled polymer microelement has an average size of 5 to 200 microns.   The plurality of polymer particles of claim 1, wherein the alkaline earth metal oxide-containing particles cover 1-40% of the outer surface of the shell of the gas-filled polymer microelement. A plurality of polymer particles embedded with an alkaline earth metal oxide,
A gas-filled polymer microelement, wherein the gas-filled polymer microelement has a shell and a density of 10 g / liter to 100 g / liter, the shell has an outer surface and a diameter of 5 μm to 200 μm; The outer surface of the shell has alkaline earth metal oxide-containing particles embedded in the polymer, the alkaline earth metal oxide-containing particles have an average particle size of 0.01-2 μm, Alkaline earth metal oxide-containing particles are dispersed in each of the polymer microelements, and the alkaline earth metal oxide-containing region coats 1-40% of the outer surface of the polymer microelements. Discrete, less than 0.1% by weight of the polymer microelements in total i) alkaline earth metal oxide-containing particles having a particle size greater than 5 μm, ii) Alkaline earth metal oxide-containing regions covering more than 50% of the outer surface of the polymer microelements, and iii) polymer microparticles aggregated with alkaline earth metal oxide-containing particles to an average cluster size greater than 120 μm A plurality of polymer particles associated with the element.   6. The plurality of polymer particles of claim 5, wherein the gas-filled polymer microelement is a copolymer of polyacrylonitrile and methacrylonitrile filled with isopentane.   6. The plurality of polymer particles of claim 5, wherein the gas filled polymer microelements have an average size of 10 to 100 microns.   6. The plurality of polymer particles of claim 5, wherein the alkaline earth metal oxide-containing particles cover 2-30% of the outer surface of the shell of the gas-filled polymer microelement.